[ntp:questions] Getting PPS on a modern rack-mounted server?

John Ackermann N8UR jra at febo.com
Thu May 29 19:32:55 UTC 2008


John Ioannidis said the following on 05/29/2008 03:10 PM:
> This may sound like an embarrassment of riches, but here is my problem: 
> I have some rack-mounted servers (IBM System x3650 to be precise) that I 
> need to synchronize with a PPS signal.  The problem is, of course, that 
> the machines have only one serial port, which I want to use as a serial 
> console, and of course they have no parallel ports.
> 
> Any suggestions?  Can I use a PCI serial card? Will that have acceptable 
> jitter?

A PCI serial card should work fine.  The main jitter source is the
interrupt latency which shouldn't be much different on a PCI card than
on the motherboard port.

<shameless_plug>
If you need to distribute the same PPS signal to a number of boxes, I
designed a board which is being sold as a kit by TAPR (we have
arrangements with someone who can assemble them for a fee, if required)
that provides up to six TTL level PPS signals, as well as two RS-232
compatible signals.  Check http://www.tapr.org/kits_tadd-3.html.
</shameless_plug>

John



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